Indoor unit for air conditioner

ABSTRACT

An air conditioner indoor unit has a box-shaped body casing  1.  A pair of air inlet ports  5  are formed in a front surface of the body casing  1.  A pair of air outlet ports  7  are formed on both sides of each of the air inlet ports  5.  A pair of air passages  6  are each formed in the body casing  1  and extend from the corresponding air inlet port  5  toward the air outlet ports  7.  Turbofans  8  are arranged in the body casing  1  in correspondence with the air inlet ports  5.  A pair of heat exchangers  9  are arranged on both sides of each of the turbofans  8  in correspondence with the associated two air outlet ports  7.  A drain pan  15  is arranged below the heat exchangers  9  and the turbofans  8.  Refrigerant pipes  21   a,    21   b,    21   c,    21   d,  which connect the heat exchangers  9  to each other, are received in the drain pan  15.

TECHNICAL FIELD

The present invention relates to a configuration of an air conditionerindoor unit that can be made slim and compact.

BACKGROUND ART

Patent Document 1, for example, discloses a conventional wall-mountedindoor unit of a general air conditioner. The indoor unit has two frontand rear drain pans, a plurality of lambdoid cross fin type heatexchangers supported on the drain pans, and a cross flow fan arrangedbetween the heat exchangers. After passing through the heat exchangers,air is blasted into a room through a scroll passage.

However, since the heat exchangers and the cross flow fan are arrangedand aligned in a front-rear direction, there is a limit on the reductionthe thickness of the indoor unit.

To solve this problem, the applicant of the present invention hasattempted to minimize the thickness of indoor units, for example, asdescribed in the indoor units of Patent Documents 2 and 3. For example,one such indoor unit includes a centrifugal fan having a small axialdimension and a pair of heat exchangers arranged on both sides of thecentrifugal fan. Each of the heat exchangers is an aluminum layeredtype, which is small in size and high in heat exchange efficiency. Afterbeing drawn from a central portion of a front surface of the indoorunit, air is blasted forward from air outlet ports, which are formed onboth sides of the indoor unit through the heat exchangers. Thisconfiguration reduces the thickness of the indoor unit.

In the layered type heat exchangers, a header and refrigerantoutlet/inlet ports are concentrated on one side of each heat exchanger,as described in, for example, Patent Document 3. Accordingly, if eachheat exchanger is arranged above the header, pipes are concentrated in alower portion of the indoor unit. If the heat exchanger is arrangedbelow the header, the pipes are concentrated in an upper portion of theindoor unit.

However, when the pipes are arranged in the upper portion, the size ofthe indoor unit must be enlarged in order to create the space foraccommodating the pipes.

Also, when the air conditioner is in cooling operation, condensed wateron surfaces of the pipes drips. It is likely that the dew drops may hita component such as a fan and be splashed to the outside of the indoorunit. If a heat insulating material is wrapped around the pipes in orderto prevent water condensation, the size of the indoor unit is furtherenlarged.

-   Patent Document 1: Japanese Laid-Open Utility Model Publication No.    5-8316-   Patent Document 2: Japanese Laid-Open Patent Publication No.    2006-29702-   Patent Document 3: Japanese Laid-Open Patent Publication No.    2006-36909

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide anair conditioner indoor unit that can be effectively made slimmer andmore compact.

To achieve the foregoing objective and in accordance with one aspect ofthe present invention, an air conditioner indoor unit is provided thatincludes a box-shaped casing, an air inlet port formed in a centralportion of a front surface of the casing, a pair of air outlet portsformed on both sides of the front surface of the casing, a pair of airpassages formed in the casing and extending from the air inlet port tothe air outlet ports, a fan that is arranged upstream from the airpassages and corresponds to the air inlet port, a pair of heatexchangers that are arranged downstream from the air passages andcorrespond to the air outlet ports, and a refrigerant pipe connectingthe heat exchangers to each other. A drain pan is arranged below theheat exchangers and the fan, and the refrigerant pipe is received in thedrain pan.

In this configuration, dew drops formed on surfaces of the heatexchangers are drained to the drain pan. The drain pan thus reliablycollects the drained water. Also, a number of refrigerant pipes, whichare concentrated below the heat exchangers, are received in the space inthe drain pan without interfering with other components.

Accordingly, it is unnecessary to create additional space for therefrigerant pipes. The indoor unit body thus can be made more compact.

Further, dew drops formed on the refrigerant pipes are collected in thedrain pan without being splashed to the outside.

The casing preferably has a back plate, and the drain pan is preferablyformed integrally with the back plate of the casing.

In this configuration, the heat exchangers and the fan are incorporatedas an integral body and unitized with the drain pan. Since the heatexchangers and the fan are received in the casing while being unitized,the indoor unit is manufactured, assembled, and maintained easily.

A partition plate is preferably arranged between the fan and the drainpan.

In this configuration, an air flow from the fan is prevented fromaffecting the refrigerant pipes and changing the phase of therefrigerant flowing in the refrigerant pipes. Further, the air flow fromthe fan is straightened by the partition plate and smoothly blastedtoward the air outlet ports, which are arranged on both sides.

The partition plate also prevents the air flow from the fan from blowingout of the outlet ports through the drain pan without passing throughthe heat exchangers.

The air blowing performance of the indoor unit is thus improved.

The two heat exchangers preferably each extend across the correspondingone of the air passages and are inclined in mutually differentdirections.

In this configuration, a necessary heat exchange surface area is ensuredin the indoor unit and the thickness of the indoor unit is minimized.Accordingly, the indoor unit becomes slimmer.

Positioning members for positioning the heat exchangers are preferablyarranged on both sides in the drain pan.

The configuration greatly facilitates the assembly of the heatexchangers with the drain pan, thus improving the production efficiency.

Stepped portions for positioning the heat exchangers are preferablyformed in a bottom portion of the drain pan.

This configuration greatly facilitates the assembly of the heatexchangers with the drain pan, thus improving the production efficiency.

Each of the stepped portions of the drain pan is preferably formed by awide portion corresponding to an upper portion of the drain pan and anarrow portion corresponding to the bottom portion of the drain pan, anda heat insulating material is preferably arranged on an outer surface ofthe narrow portion formed in the bottom portion of the drain pan.

This configuration allows the insulating material to be easily mountedand attached, and the stepped portions are used further effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an air conditioner indoor unit, asa whole, according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view showing the indoor unit illustrated inFIG. 1 with a front cover in an open state;

FIG. 3 is a cross-sectional plan view showing the indoor unit of FIG. 1;

FIG. 4 is a perspective view showing the internal structure of theindoor unit of FIG. 1;

FIG. 5 is a perspective view showing the configuration of a main heatexchanger of the indoor unit of FIG. 1;

FIG. 6 is a perspective view showing the configuration of an auxiliaryheat exchanger of the indoor unit of FIG. 1;

FIG. 7 is a perspective view showing the arrangement of refrigerantpipes in the indoor unit of FIG. 1;

FIG. 8 is a perspective view showing the refrigerant pipes illustratedin FIG. 7 in a state received in a drain pan;

FIG. 9 is a plan view showing the configuration of a positioning portionof the heat exchanger of the indoor unit of FIG. 1;

FIG. 10 is a longitudinal cross-sectional view showing the positioningportion illustrated in FIG. 9;

FIG. 11 is a longitudinal cross-sectional view showing the positioningportion of FIG. 9 as viewed from the side;

FIG. 12 is a longitudinal cross-sectional view showing the indoor unitof FIG. 1 with a partition plate installed, as viewed from the front;

FIG. 13 is a plan view showing a positioning portion of a heat exchangerof an air conditioner indoor unit according to a second embodiment ofthe present invention;

FIG. 14 is a longitudinal cross-sectional view showing the positioningportion illustrated in FIG. 13;

FIG. 15 is a longitudinal cross-sectional view showing the positioningportion of FIG. 13 as viewed from the side;

FIG. 16 is a cross-sectional view showing the configuration of a heatinsulating material bonded to a lower surface of the positioning portionof FIG. 13;

FIG. 17 is a perspective view showing an example of the layout ofrefrigerant pipes of an air conditioner indoor unit according to thepresent invention;

FIG. 18 is a perspective view showing the configuration of the interiorof an air conditioner indoor unit, as a whole, according to a thirdembodiment of the present invention;

FIG. 19 is a perspective view showing the arrangement of refrigerantpipes of the indoor unit illustrated in FIG. 18; and

FIG. 20 is a perspective view showing the refrigerant pipes illustratedin FIG. 19 received in a drain pan as in the state (the integratedstate) illustrated in FIG. 8.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

The configuration of an air conditioner indoor unit according to a firstembodiment of the present invention will now be described with referenceto FIGS. 1 to 12.

As illustrated in FIGS. 1 to 3, the air conditioner indoor unit is atwin type formed by a pair of indoor subunits that are arranged side byside. The indoor subunits each include a fan and two heat exchangers,which are arranged on both sides of the fan.

The air conditioner indoor unit has a flat cassette type body casing 1,which is elongated in a lateral direction and thin in a front-reardirection. The body casing 1 is formed by a back panel (a back plate) 1a, two side panels (side plates) 1 b, a front panel (a front plate) 1 c,an upper panel (a top plate) 1 d, and a bottom panel (a bottom plate) 1e. The back panel 1 a forms an attachment surface to which fan motors 8b of turbofans 8, which will be described later, are attached.

Out of these panels 1 a, 1 b, 1 c, 1 d, 1 e, the panels 1 b, 1 c, 1 d, 1e, except for the back panel 1 a, are formed by a single continuousplate.

The two indoor subunits, which are arranged adjacent to each other, areformed identically. Accordingly, only one of the indoor subunits will bedescribed.

As illustrated in FIG. 3, a circular air inlet port 5, which functionsas a bellmouth, is formed in a central portion of a part of the frontpanel 1 c that forms one of the indoor subunits. A turbofan 8 serving asa centrifugal fan, which has a small depth, is arranged inside the airinlet port 5.

Each turbofan 8 has a main plate 8 d, a shroud 8 c, and a plurality ofblades 8 a (an impeller), which are arranged between the shroud 8 c andthe main plate 8 d.

A pair of rectangular air outlet ports 7, each of which has apredetermined width and extends in a vertical direction, are formed onboth sides of each air inlet port 5 of the front panel 1 c. The two ofthe air outlet ports 7 that are arranged adjacent to each other in acentral portion of the body casing 1 are formed as a common outlet portfor the two adjacent indoor subunits.

In the body casing 1, two air passages 6 extend from each air inlet port5 having the bellmouth structure and separate toward the correspondingair outlet ports 7, which are arranged on both sides of the air inletport 5. The turbofan 8 corresponding to the shroud 8 c is formed in theair passages 6 and at the back of the air inlet port 5. Specifically,the turbofan 8 is received in the air inlet port 5 with a clearancearound the turbofan 8. The turbofan 8 is attached to the back panel 1 aof the body casing 1 with the fan motor 8 b, which is arranged insidethe impeller.

As illustrated in FIG. 4, for example, the back panel 1 a has anecessary height H and is formed integrally with a back plate 16 of adrain pan 15, which is located below the back panel 1 a (the back panel1 a is formed by extending the back plate 16, which is the same plateforming the back panel 1 a, upward).

With reference to FIG. 3, a pair of heat exchangers 9 are located onboth sides of each turbofan 8 in the air passages 6. The heat exchangers9 are located at the positions corresponding to the air outlet ports 7,which are arranged below the air passages 6. The two heat exchangers 9are arranged in the corresponding two air passages 6, which extend fromthe central portion of the body casing 1 toward both sides, in such amanner that the heat exchangers 9 extend across the corresponding airpassages 6 and greatly incline in mutually different directions.

As has been described, the two heat exchangers 9 are greatly inclinedwith respect to the corresponding air passages 6. Accordingly, as isclear from FIG. 3, a necessary heat exchange surface area is effectivelyensured, and the width (the depth) of the indoor unit body in thefront-rear direction is minimized. As a result, the indoor unit body ismade slimmer.

In the present embodiment, as illustrated in, for example, FIG. 5, eachof the heat exchangers 9 is formed by a compact aluminum layered typeheat exchanger, which includes flat heat transmission pipes (porouspipes) 9 a and flat heat-transfer fins (which are, for example,corrugated fins) 9 b and exhibits extremely high heat transmissionperformance. A pair of refrigerant headers 20 (20 a, 20 b) are arrangedbelow each heat exchanger 9. A plurality of refrigerant pipes 21 a, 21b, 21 c, 21 d (see FIG. 7) are connected to the correspondingrefrigerant headers 20 (20 a, 20 b) in a concentrated manner.

As illustrated in, for example, FIGS. 4 and 9 to 11, each heat exchanger9 is supported with the refrigerant headers 20, which are arranged atthe lower end of the heat exchanger 9, received in the drain pan 15.Specifically, the refrigerant headers 20 are fixed and accuratelypositioned at predetermined positions on a bottom surface 15 a of thedrain pan 15 by positioning members 22, 23. In this manner, the heatexchangers 9 are supported by and integrated with the drain pan 15.

The positioning members 22, 23 include positioning members 22 a, 23 a,22 b, 23 b. The positioning members 22 a, 23 a each have a small heightin the vertical direction. The height of each positioning member 22 b,23 b is greater than the height of each positioning member 22 a, 23 a.The positioning members 22 b, 23 b each include a tapered surface forsetting the inclination angle of the heat exchanger 9. Recesses 22 c, 23c are each formed by the corresponding positioning members 22 a, 23 a,22 b, 23 b and the inner surface of the drain pan 15. Each one of therecesses 22 c, 23 c is fixedly engaged with the end portion and theouter peripheral portion of the corresponding one of the refrigerantheaders 20, which corresponds to the front or rear corner of the heatexchanger 9. The recesses 22 c, 23 c are formed in correspondence withthe inclination angles of the corresponding heat exchangers 9.

Accordingly, by pressing the refrigerant headers 20 of each heatexchanger 9 into the recesses 22 c, 23 c in such a manner as to engagethe refrigerant headers 20 with the recesses 22 c, 23 c as illustratedin FIGS. 9 to 11, the heat exchanger 9 is easily installed in a stablestate at a desired height and a desired inclination angle.

Further, in the present embodiment, as illustrated in FIGS. 4 and 7, forexample, a pair of supercooling heat exchangers 19 are provided. Thesupercooling heat exchangers 19 function as condensers when the airconditioner is in heating operation and as evaporators when the airconditioner is in cooling operation. The two supercooling heatexchangers 19 are arranged substantially symmetrically between eachturbofan 8 and the heat exchangers 9 arranged on both sides of theturbofan 8. With reference to FIG. 6, each of the supercooling heatexchangers 19 is configured as a small-sized cylindrical heat exchangerwith fins, which is configured simply by wrapping a spine fin 19 aaround a heat exchange tube 21 d, which is a continuous refrigerantpipe. Each supercooling heat exchanger 19 is arranged in such a mannerthat the heat exchange tube 21 d extends in the vertical direction.

In the body casing 1, a vacuum heat insulating material 10 is bonded tothe inner surfaces of the back panel 1 a, the side panel 1 b, and thefront panel 1 c, which face each heat exchanger 9. Each of the vacuumheat insulating materials 10 is flat and a vacuum is formed in thevacuum heat insulating material 10. With reference to, for example,FIGS. 16, which will be explained below, each vacuum heat insulatingmaterial 10 has a hollow synthetic resin sheet 10 a and an aluminum foil10 c. The inside of the resin sheet 10 a is filled with a shaperetaining glass wool 10 b. The aluminum foil 10 c is bonded to the outerperiphery of the sheet 10 a.

As has been described, in the present embodiment, the heat exchangers 9,each of which is a compact aluminum layered type and has a high heatexchange efficiency, are arranged on both sides of the correspondingturbofan 8 in the inclined state. After being drawn through each airinlet port 5, which is arranged in a front central portion, air isblasted forward from the air outlet ports 7 on both sides. Thisconfiguration minimizes the thickness of the indoor unit body. Further,as illustrated in FIG. 4 (a view from front) and FIG. 8 (a view frombehind without the portion corresponding to the back plate 16), thedrain pan 15 (the bottom surface 15 a), which is shaped like a plate andextends in correspondence with the entire portion of the indoor unitbody, is arranged below the two heat exchangers 9 and the associatedturbofan 8. A large number of refrigerant pipes 21 a to 21 d connectedto the corresponding heat exchangers 9 are accommodated in the drain pan15 using the vacant space in the drain pan 15 having a predetermineddepth.

That is, as has been described, in each heat exchanger 9, which is thelayered type, the refrigerant headers 20 and the inlet and outlet portsof the refrigerant pipes 21 a to 21 d are concentrated on one side ofthe heat exchanger 9. Accordingly, if the heat exchangers 9 are arrangedabove the refrigerant headers 20 as illustrated in FIG. 7, therefrigerant pipes 21 a to 21 d are concentrated below the heatexchangers 9. Contrastingly, if the heat exchangers 9 are arranged belowthe refrigerant headers 20 as illustrated in FIG. 17, the refrigerantpipes 21 a to 21 d are concentrated above the heat exchangers 9. In thiscase, the indoor unit body must be enlarged in size to ensure the spacefor accommodating the pipes. Also, when the air conditioner is incooling operation, dew drops formed on the refrigerant pipes may dripand hit a structure such as a fan, and thus may be splashed to theoutside of the unit. If a heat insulating material is wrapped around thepipes to prevent dew condensation, the size of the indoor unit will befurther enlarged.

To solve this problem, in the present embodiment, the drain pan 15 isarranged below the two heat exchangers 9, which are arranged for eachturbofan 8, and the turbofan 8, with reference to FIGS. 4 and 8, forexample. The drain pan 15 receives the refrigerant pipes 21 a to 21 d,which connect each pair of heat exchangers 9 together. In this manner,all of the pipes are received in the drain pan 15, thus solving theabove-described problem.

In this configuration, the condensed water on the surfaces of the heatexchangers 9 is drained to the drain pan 15. The drain pan 15 thusreliably collects the condensation water. Further, a large number ofrefrigerant pipes 21 a to 21 d, which are concentrated below the heatexchangers 9, are accommodated in the vacant space in the drain pan 15without interfering with other components.

Accordingly, it is unnecessary to create additional space for the pipes.This further reduces the size of the indoor unit body in size.

Also, dew drops formed on the refrigerant pipes 21 a to 21 d arecollected directly by the drain pan 15 without being splashed to theoutside.

In the above-described configuration, the drain pan 15 is formedintegrally with the back panel 1 a of the indoor unit casing, as hasbeen described.

Since the drain pan 15 is formed integrally with the back panel 1 a ofthe indoor unit casing, using which the turbofans 8 are mounted, theheat exchangers 9 and the associated turbofan 8 are incorporated as anintegral body and unitized with the drain pan 15. Accordingly, whilebeing unitized, the drain pan 15, the heat exchangers 9, and theturbofans 8 are accommodated in the body casing 1 of the indoor unit asan integral body. This facilitates the assembly, manufacture, andmaintenance of the indoor unit.

However, when the above-described configuration is employed, it isnecessary to partition the air chamber of each turbofan 8 from the spacein the drain pan 15 in some way. Specifically, through suchpartitioning, the air flow from the turbofan 8 must be smoothlystraightened toward the corresponding air outlet ports 7 and preventedfrom affecting the refrigerant pipes 21 a to 21 d in order to preventchange of the phase of the refrigerant.

It is also necessary to prevent the air flow from each turbofan 8 fromblowing out of the air outlet ports 7 through the drain pan 15 withoutpassing through the corresponding heat exchanger 9.

To satisfy these needs, in the present embodiment, a partition plate 17is arranged in such a manner as to separate the turbofans 8 and the heatexchangers 9 from the drain pan 15 (and the refrigerant pipes 21 a to 21d), as illustrated in FIG. 12. This prevents the refrigerant pipes 21 ato 21 d from being cooled by the air flow from the turbofans 8. Also, byshaping the partition plate 17 as needed in correspondence with theshape of each turbofan 8, flow straightening performance is improved sothat air blowing performance is improved. Although the partition plate17 is flat in the present embodiment, the partition plate 17 may beformed in an arcuate shape or a scroll shape.

In this configuration, the partition plate 17 prevents the air flowsfrom the turbofans 8 and the heat exchangers 9 from affecting therefrigerant pipes 21 a to 21 d. Accordingly, the phase of therefrigerant flowing in the refrigerant pipes 21 a to 21 d is preventedfrom changing.

Further, the partition plate 17 smoothly straightens the air flow fromeach turbofan 8 toward the air outlet ports 7, thus improving the airblowing performance of the turbofan 8. This improves the heat exchangeefficiency of each heat exchanger 9.

Also, the partition plate 17 prevents the air flow from each turbofan 8from blowing out of the air outlet ports 7 via the drain pan 15 withoutpassing through the corresponding heat exchanger 9.

Additionally, in the present embodiment, front covers 2, 3 are arrangedat the front side of the front panel 1 c as necessary, as illustratedin, for example, FIGS. 1 and 2. In this case, for example, the twocenter front covers 2 cover the air inlet ports 5 and the air outletports 7 at the center. The two front covers 3 on both sides each coverthe corresponding one of the air outlet ports 7, which are located onboth sides of the body casing 1.

The center front covers 2 are each supported by a support member 21,which is configured as, for example, a link, in such a manner that eachfront cover 2 is selectively opened and closed in the front-readdirection (or a direction inclined with respect to the front-reardirection). When the front covers 2 are open, as illustrated in FIG. 2,air is drawn into the air inlet ports 5 from above and below in thevertical direction. In this state, the common air outlet ports 7, whichare located at the center, are held open and the air is blown out of theair outlet ports 7.

In contrast, each of the front covers 3 on both sides is supported by ahinge structure in such a manner that each front cover 3 is selectivelyopened and closed. When the front covers 3 are open, the air outletports 7 on both sides of the casing are held open and the air is blownout of the air outlet ports 7.

If the front covers 2, 3 are all closed as illustrated in FIG. 1, theindoor unit as a whole forms a simple slim cabinet structure having aflat front surface.

Second Embodiment

The configuration of an air conditioner indoor unit according to asecond embodiment of the present invention will hereafter be explainedwith reference to FIGS. 13 to 16.

The second embodiment is different from the first embodiment in that thedrain pan 15 includes stepped portions 15 b. Specifically, positioningmembers 24, 25 for setting inclination angles are arranged in the drainpan 15. The stepped portions 15 b are formed in a lower portion of thedrain pan 15, with reference to FIGS. 13 to 15. The upper steppedsurface of each stepped portion 15 b functions as a positioning memberfor a height direction. Each stepped portion 15 b is formed by a wideportion corresponding to an upper portion of the drain pan 15 and anarrow portion corresponding to a bottom portion of the drain pan 15. Avacuum heat insulating material 10 having a minimized thickness isarranged at the outer surface of the narrow portions of the steppedportions 15 b (the outer surface of the bottom portion of the drain pan15), as illustrated in, for example, FIG. 16.

The vacuum heat insulating material 10 is formed by, for example, ahollow sheet 10 a formed of synthetic resin and an aluminum foil 10 c.The inside of the hollow sheet 10 a is filled with a shape retainingglass wool 10 b. The aluminum foil 10 c is bonded to the outer peripheryof the sheet 10 a.

Typically, a heat insulating material is bonded to the drain pan 15 inorder to prevent dew condensation. However, to provide a slim indoorunit such as the above-described one, it is required to decrease thethickness of the heat insulating material (particularly in the frontside and the backside), too. To meet this requirement, the positioningmembers 22 b, 23 b of the above-described first embodiment are replacedby the stepped portions 15 b formed in the drain pan 15. Each steppedportion 15 b functions as positioning means for the height direction.Further, by bonding the heat insulating material 10 to the outer surfaceof the stepped portion 15 b, the heat insulating material 10 isprevented from projecting outward with respect to the outer surface ofthe drain pan 15 as much as possible.

The other portions of the second embodiment are configured identicallyto the corresponding portions of the second embodiment. The secondembodiment has the same advantages as those of the first embodiment.

Third Embodiment

The configuration of an air conditioner indoor unit according to a thirdembodiment of the present invention will now be described with referenceto FIGS. 18 to 20.

The third embodiment is characterized in that each supercooling heatexchanger 19 of the first embodiment is configured by a flat cross fincoil type supercooling heat exchanger 19, which is illustrated in, forexample, FIGS. 18 to 20, instead of the heat exchanger having thecylindrical spine fin.

Through such configuration, the supercooling heat exchange efficiency isfurther improved.

Specifically, the thickness of the cross fin coil type supercooling heatexchanger 19 is significantly less than the aforementioned spine fintype supercooling heat exchanger. This configuration saves space andreduces the pressure loss of each turbofan 8, thus raising heat exchangeperformance by 50% or more for a constant fan resistance. Accordingly,the supercooling heat exchange efficiency is improved.

For the cross fin coil type supercooling heat exchangers 19, refrigerantpipes 21 d having U-shaped pipe structures may be employed. This makesit possible to arrange all of the refrigerant pipes 21 a to 21 dextending from the refrigerant headers 20, which include the refrigerantpipe 21 d connecting the adjacent supercooling heat exchangers 19 toeach other, in the drain pan 15. This allows all of the refrigerantpipes 21 a to 21 d to be accommodated in the drain pan 15, and thusbrings about the advantage that the indoor unit is further reduced insize. Also, dew drops formed on the surfaces of the refrigerant pipes 21a to 21 d are completely prevented from being splashed to the outside ofthe indoor unit.

In each cross fin coil type supercooling heat exchanger 19, a plate finextends perpendicular to a heat transmission pipe. When the supercoolingheat exchanger 19 is installed to be upright, the portion correspondingto the plate fin is arranged horizontally, thus causing a minor problemabout water drainage.

To promote the water drainage of the plate fin, it is preferable toinstall each supercooling heat exchanger 19 in a slanted manner so thatthe supercooling heat exchanger 19 is slightly inclined in a horizontaldirection with respect to a vertical direction, instead of installingthe supercooling heat exchanger 19 linearly in the vertical direction.

The other portions of the third embodiment are configured identically tothe corresponding portions of the first embodiment. The third embodimenthas the same advantages as those of the first embodiment.

1. An air conditioner indoor unit comprising a box-shaped casing, an airinlet port formed in a central portion of a front surface of the casing,a pair of air outlet ports formed on both sides of the front surface ofthe casing, a pair of air passages formed in the casing and extendingfrom the air inlet port to the air outlet ports, a fan that is arrangedupstream from the air passages and corresponds to the air inlet port, apair of heat exchangers that are arranged downstream from the airpassages and correspond to the air outlet ports, and a refrigerant pipeconnecting the heat exchangers to each other, the air conditioner indoorunit being characterized by a drain pan arranged below the heatexchangers and the fan, the refrigerant pipe being received in the drainpan.
 2. The air conditioner indoor unit according to claim 1,characterized in that the casing has a back plate, the drain pan beingformed integrally with the back plate of the casing.
 3. The airconditioner indoor unit according to claim 1 or 2, characterized in thata partition plate is arranged between the fan and the drain pan.
 4. Theair conditioner indoor unit according to claim 1, characterized in thatthe two heat exchangers each extend across the corresponding one of theair passages and are inclined in mutually different directions.
 5. Theair conditioner indoor unit according to claim 1, characterized in thatpositioning members for positioning the heat exchangers are arranged onboth sides in the drain pan.
 6. The air conditioner indoor unitaccording to claim 1, characterized in that stepped portions forpositioning the heat exchangers are formed in a bottom portion of thedrain pan.
 7. The air conditioner indoor unit according to claim 6,characterized in that each of the stepped portions of the drain pan isformed by a wide portion corresponding to an upper portion of the drainpan and a narrow portion corresponding to the bottom portion of thedrain pan, a heat insulating material being arranged on an outer surfaceof the narrow portion formed in the bottom portion of the drain pan.